In wireless communications, a non-linearity problem of a PA (power amplifier) restricts a maximum transmit power and efficiency of the PA. In order to improve the transmit power and efficiency of the PA to a maximum extent, a pre-distortion technology may be adopted to offset non-linearity of the PA, so as to enable the PA to work in a non-linear amplification region, thereby improving the transmit power and efficiency of the PA. The pre-distortion technology refers to that, pre-distortion processing is performed for a signal before the signal is input to a PA, to obtain a distorted signal, and the distorted signal will offset non-linearity of the PA when passing through the PA, thereby implementing linearity of the PA and improving a transmit power and efficiency of the PA.
In the pre-distortion technology, a pre-distortion coefficient plays a key role. An optimal linear effect of the PA can be achieved by selecting a pre-distortion coefficient which best matches a current output power of the PA. Currently. The pre-distortion coefficient mainly includes two types, namely, an open-loop pre-distortion coefficient and a closed-loop pre-distortion coefficient.
Regarding the open-loop pre-distortion coefficient, outputs under different transmit powers in a non-linearity region of a PA are sampled by using a dedicated instrument (for example, a spectrum analyzer) before a device (for example, a transceiver) leaves the factory, a group of pre-distortion coefficients corresponding to the transmit powers of the PA is obtained by using a computer, and the group of pre-distortion coefficients is written into a memory of the device. When the device is in actual use, a pre-distortion coefficient corresponding to a transmit power currently set by the device is directly selected from the memory to perform pre-distortion processing for a signal, so as to solve a non-linearity problem of the PA. However, with temperature variations and PA aging, an actual transmit power of the device may deviate from the currently set transmit power, which causes deviation of a correspondence between the set transmit power and an open-loop pre-distortion coefficient, making a pre-distortion effect poor.
Different from the open-loop pre-distortion coefficient, regarding the closed-loop pre-distortion coefficient, a pre-distortion coefficient calculating apparatus (mainly including a sampling circuit, a frequency converter, a filter, an analog to digital converter, and the like) is integrated on a device (for example, a transceiver), and the calculating apparatus is used to sample outputs of the PA in real time, so as to calculate a pre-distortion coefficient which best matches a current transmit power, thereby achieving an optimal pre-distortion effect. However, in this manner, the pre-distortion coefficient calculating apparatus such as the sampling circuit, the frequency converter, the filter, and the analog to digital converter needs to be added to each device, which significantly increases a manufacturing cost.